Ballast transformer apparatus



Oct. 25, 1960 w. J. KARAsH BALLAST TRANSFQRMER APPARATUS Filed May 7, 1959 United States Patent C) f' BALLAST TRANSFORMER APPARATUS Walter J. Karash, lCleveland, Ohio, assignor to General Electric Company, a corporation of New York Filed May 7, 1959, Ser. No. 811,651

Claims. (Cl. 315-100) This invention relates to electric lighting systems and more particularly to systems for starting and operating electric discharge lamps.

u Discharge lamps, such as the residential and commercial uorescent larnps, have a negative resistance characteristic; that is, once the lamp has started, the apparent impedance of the lamp diminishes. For this reason, it is necessary to provide a means of limiting the current flow through the lamp after starting thereof in order that the lamp does not destroy itself. It is also frequently necessary -to impress a relatively high voltage on the lamp during `starting thereof in order to initiate the discharge. Once :the discharge through the lamp has been initiated, the high starting voltage is not needed, and may be undesirable. A single high impedance ballast transformer is normally provided to supply the required high starting voltage and to limit the current flow after the lamp has started.

In the co-pending application of Charles E. Strecker, Serial No. 435,753, iiled June l0, 1954 and assigned to the same assignee as the present invention, there is disclosed a ballast apparatus in which a high voltage starting aid circuit is efI'ected for initially ionizing the gas in the discharge lamp. The apparatus includes a primary winding and a secondary Winding with the primary and secondary connected in series in the starting aid circuit s0 that their voltages are additive. However, once the lamp starts, it is then operated by the vol-tage of the secondary alone, with the secondary being in a substantially isolated relationship relative to the primary.

During starting, the Strecker starting aid circuit includes the primary winding and the secondary winding in autotransformer relation with theirvoltages additive, applied to one electrode of the discharge lamp which is in capacitivey relation with the conducting fixture, with the circuit being completed through ground, or other connection, from the conducting fixture to the low potential side of the primary winding or supply line. In this manner, the additive vol-tages of the primary and secondary windings are applied to one of the electrodes during starting. A small amount of current will ow in this circuit from the electrode -to the fixture thereby ionizing the gas in the area of the electrode. The high voltage of the secondary winding is concurrently placed across the electrodes of the lamp and this, together with the ionization of the gas in the lamp, causes the lamp to start. Once the lamp has started, the current flow in the circuit from the electrode to the conducting fixture is minor With reference to the current ilow across the electrodes of the lamp due to the high capacitive impedance of the coupling of the lamp and the fixture; the lamp will then be in circuit relation with the secondary of the transformer. The transformer will operate the lamp as a substantially isolated secondary transformer.

In the aforementioned Strecker application, as a safety precaution it was desirable to connect the low potential side of the secondary winding with the high potential side of the primary winding by means of a line containing 2,958,007 Patented Oct. 25, 1960 a fairly high resistance. This resistance Was desirable in order to limit the current flow in the starting aid circuit to a safe value. Such a restriction was felt to be necessary so that if one handling the device comes in contact with the high voltage terminal and the ground, or with the high voltage terminal and the lamp contacts, the lamp will not fire and a lethal current would not flow..

However, since a current flows in the starting aid cir-y cuit, any high resistance in -this circuit creates a Voltage drop which decreases the voltage available for starting` aid potential. In some instances, it may be desirable, and, in fact, necessary, to apply the maximum starting aid potential available :to the lamp electrode during start ing. In such instances, the high resistance between the primary winding and the secondary winding would be undesirable.

Moreover, ballast design is generally dictated by the economies involved. The addition of a high resistance between the primary winding and the secondary winding necessarily adds `to the cost of the ballast, and is therefore undesirable where it is not needed for safety purposes.

According to the instant invention, the desired safety features are incorporated into a lighting system of the type including a starting aid circuit, without the use of the high resistance in the line connecting the low potential side of the secondary winding and the high potential side of the primary winding.

This invention thus has as its primary object the provision of an improved electrical system for igniting and operating gaseous discharge devices, wherein a high voltage is applied as a starting aid, and safety features are provided without the use of high resistance.

Another object of this invention is to provide an improved electrical system of this type for igniting a pair of gaseous discharge lamps at high voltage and then thereafter operating the same at reduced voltage.

According to the instant invention7 therefore, a lighting; system is provided comprising at least one gaseous discharge lamp connected `to la ballast transformer apparatus. The ballast transformer apparatus includes a magnetic core having a primary winding and a secondary winding connected in autotransformer relation, with their voltages laddi-tive, by a line having no substantial impedance. 'Ille combined voltages of the windings are lapplied to one cathode of the lamp in a starting aid circuit through the capacitive coupling between the lamp and its associated fixture, and with no impedance between the windings the starting aid current is limited primarily only by the impedance lof the capacitive coupling. After starting, the lamp is operated by the secondary alone in a closed secondary circuit.

The desired safety is provided by the physical arrangement of the lamp in its holder. The lamp is the common double ended type, which may have preheatable electrodes mounted in each end of a tubular glass envelope. The electrodes each have a pair of inlead wires extending through the glass envelope to a lamp base. The lamp base has the inlead wires recessed and thereby the inleads are protected from accidental contacts by one who may be handling the lamp. (Such a lamp base is described and claimed in U.S. Patent No. 2,716,739, issued August 30, 1955, to Eugene Lemmers, and assigned to the same assignee as the present invention). The lamp is supported in lamp holders having recessed contacts engageable with the recessed inlead wires of the base, thereby preventing accidental contact with the lamp holder contacts. (Such a lamp holder is disclosed and claimed in U.S. Patent No. 2,716,738, issued August 30, 1955, to John M. Pistey, and assigned to the same assignee as the instant invention.) Since the inleads of the lamp and the contacts of the base are protected from accidental contact, a current limiting impedance in the high voltage starting aid circuit is not needed, and thereby a practically effective starting aid circuit is provided.

VThe invention together with additional objects and advantages will best be understood from the following description of specific embodiments, when read in connection with the accompanying drawings, in which:

Fig. l illustrates the improved electrical lighting system, showing the lamp and lamp holders diagrammatically and illustrating the electrical circuit schematically; and

Fig. 2 is a front view of a lamp base of the type employed in the instant invention.

Fig. 3 is a schematic diagram of a lighting system according to the instant invention for operating a pair of serially connected discharge lamps. Referring to Fig. l of the drawings, the lamp L has a tubular glass envelope 1 provided with bases 2 and 3 attached to its ends and supported between a pair of lamp holders 4 and 5 attached to a suitable support (not shown). The lamp L is in close proximity to an elongated conducting part, here shown as the lamp fixture 6, and is thereby capacitively coupled therewith. The holder 4 is provided with a movable spring pressed hollow contact support member in the form of a plunger 7 engaging the base 2 of the lamp. To mount the lamp L in the holders, the base 2 is first engaged with the plunger 7 and the lamp L is then moved to the left to force the plunger 7 into the holder 4 until the opposite base 3 can clear the lamp holder 5. The lamp is then brought into line with the holder and the base 3 engaged with the holder 5. The lamp is held firmly in thev holders by the spring pressed plunger 7. Removal of the lamp from the holders is accomplished by moving it to the left until its base 3 is withdrawn from holder 5, tilting the lamp to clear the holder 5, and then withdrawing the base 2 from the plunger 7. The bases 2 and 3 are of identical structure and the internal parts of only the base 2 have been shown completely for conciseness in description.

Referring to Figs. l and 2, the base 2 comprises Ian annular metal shell 8, which is suitably made of sheet aluminum, and a disk 9 of electrically insulating material, such as an organic plastic. The disk 9 may be made of commercial plastic molding compounds such as those comprising phenol-furfural resins or phenolic resins. The inner rim of the shell 8 is imbedded in the periphery of the insulating disk 9 to mechanically join the members. The base 2 is secured to the end of the glass envelope 1 by a body of basing cement 10. The disk 9 has a raised elongated embossment 11 extending across its center and projecting outwardly from the base. A passage 12 is provided in the embossed portion of the disk 9 and extends completely through the center of the disk. The metal wire current inleads 13 and 14 have their inner ends connected to electrode 15 and extend through the press 16 of the stem 17 of the glass envelope 1 and into the passage 12. The elongated embossment 11 on disk 9 of the base 2 has straight parallel sides and rounded ends and the central passage 12 through the disk conforms in shape generally to that of the embossment. The outer face of the embossment is recessed to dene cavities 18 and 19 spaced from the central passage 12. Grooves 20 connect the passage 12 with each of the cavities 18 and 19. The end leads 13 and 14 of the lamp extend in spaced relation through the central passage 12 and the outer ends thereof are bent over in opposite direction to lie in the grooves 20 and terminate within the cavities 18 and 19 respectively.

The outer end portions of the wire end leads13 and 14 lying in the grooves 20 are exposed for engagement with socket contacts, but are recessed within the base, because the depth of the grooves 20 is greater than the diameter of the inleads 13, 14. As shown, the outer ends of the leads 13 and 14 lie well back of the outer end of the embossment 11, and the pass-age 12 and the grooves 20 are made too narrow for the inleads 13 and 14 to be touched accidentally in handling of the lamp incident to its insertion and removal from the lamp holder. The protection is afforded even though one end of the lamp is connected to the ballast transformer apparatus.

An electrode 21 is mounted in the other end of the lamp, and is connected to inleads 22, 23 in a base 3 of similar design as base 2. The lamp envelope 1 contains a starting gas such as argon at a few millimeters pressure and a small quantity of mercury 24 which is at a pressure of about l0 microns during operation of the lamp. A coating 25 of fluorescent material is provided on the inner surface of the envelope 1 and this material is excited to luminescence by the intense emission of 2537 A. radiation of the mercury vapor discharge during operation of the lamp.

The lamp holder. 4 shown at the left of Fig. 1 .comprises a body portion 26 providing a housing 27 through which extends the plunger 7. An internal flange ,28 is provided at the Vopening of housing 27 which acts as a stop for the spring biased plunger 7. The plunger 7 is provided with a shoulder 29 which is biased against the flange 28 by a pair of conductive springs 30 and 31. The springs 30 and 31 engage studs 32 and 33 on the back wall of the housing 27 and also studs on the at metal contacts or terminals 39 and 40. The contacts 39 Iand 40 are urged against a transverse integral partition 41 in plunger 7 by the springs 30 and 31, thereby biasing the plunger outward of the housing 27. In addition to the transverse partition 41 which acts as a stop for the contacts 39 and 40, the plunger 7 is provided with longitudinally extending partition 42 lof. electrically insulating material which extends through a slot in partition 41 and insulates from each other the springs 30 and 31 and the contacts 39 and 40. The flat portions of the contacts 39 and 40 extend through a slot in the partition 41 and into the opening 43 in the front face of the plunger 7. The back surface of the partition 41 is slanted so that the outer end portions of contacts 39 and 40 engaging inleads 13 and 14 of the base 2 are moved outwardly from each other when the embossment 11 on the lamp base 2 is withdrawn from the cavity of the plunger 7. The springs 30 and 31 in holder 4 thus serve the dual purpose of biasing the plunger 7 outward of the housing 24 and biasing the outer ends of the contacts 39 and 40 outwardly from each other to the end that the said contacts make a positive connection with the inleads 13 and 14 of the inserted base 2. The springs 30 and 31 are connected to terminal posts, shown schematically at 44 and 45 and thus also serve to conduct electrical energy to the mounted lamp.

The lamp holder 5 is similar in construction to the holder 4 except that in the holder 5 the part 46 corresponding to the movable plunger 7 of the holder 4, while of the same structure as the plunger 7, is made stationary in the housing 47 by the insertion of spacers 48 between the shoulder 49 on the part 46 and the internal flange 50 at the opening of housing 51. The part 46 thus constitutes la hollow plug in the housing 51 of Vthe holder 5. The metal springs 52, 53 corresponding to the springs 30 and 31 of the holder 4 are, of course, shorter in length than springs 27 and 28, but serve the same purpose with respect to the contacts of holder 5 as they did in holder 4. The springs 52 and 53 serve to bias contacts 54 and 55 positively against inleads 22 and 23, and have their other end connected to terminal posts sho/wn schematically at 56 and 57 and thereby also serve to form an electrical circuit to the cathode 21 at the right end of lamp 1.

The openings in plunger 7 and in plug 46 are each dimensioned to receive the embossment 11 on the bases 2 and 3, respectively, with the sides of the openings engaging the sides of the embossments 11 to support the lamp in the holders 4 Yand 5. The portions of the holder acssoov contacts in the cavities are recessed from the cavity openings so that the outer ends of the partitions lie in the openings. The fingers of a person mounting or dismounting a lamp while the lamp circuit may be unintentionally energized are thereby protected from accidentally touching electrically charged contacts of the holders 4 and 5.

The ballast transformer apparatus to ignite and operate the discharge lamp includes a magnetic core 58 within a conductive housing or a case 59. A primary winding 60 and secondary winding 61 are positioned on the magnetic core 58. Secondary cathode heating windings 62 and, 63 are formed as extensions of the secondary winding 61; but may, as readily known, be of the isolated secondary type. The low potential side of the secondary 61 is connected to the high potential side ofthe primary 60 in autotransformer relation with their voltages additive, by a line 64 having no significant impedance. The cathode heating secondary 62 has a pair of lines 65, 66 connected to terminal bases 57, 56 respectively and thereby connecting the cathode heating winding 62 in electrical circuit for supplying cathode heating energy to cathode 21 of the lamp L. Cathode heating secondary 63 has a pair of leads 67, 68 connected to base terminals 45, 44, respectively, and thereby connecting cathode heating secondary 63 to cathode of the lamp in electrical circuit for supplying cathode heating current to cathode 15. The lamp L is also electrically connected across secondary winding 61 by these leads.

A pair of leads 69, 70 extend from the end of the primary 60 for connection to a source of alternating current voltage 71, 72; the low side of which is normally, but not necessarily, grounded as illustrated by ground 73. The conducting fixture 6 is likewise normally, but not necessarily, grounded as indicated by ground 74. It is, however, necessary that the conductive fixture 6 be connected to the low potential side of primary 66 either through ground or some other connection.

In the lighting system as normally installed, this is accomplished through grounds '73, 74. lf either the conducting fixture 6, or the low potential side 72y of the alternating current voltage source is not grounded, it is merely necessary to place the conducting fixture 6 in electrical circuit with the low potential side of the primary winding 60. Such a circuit may be assured by the connection of lead 76 to the ballast case 59 as indicated by line 75. The ballast case 59 is normally grounded as indicated by ground 76, by direct connection to conducting fixture 6 thereby placing the conducting fixture 6 in electrical circuit with the low potential lead 7i) of the primary winding 6ft. It may be desirable, but not necessary, to have a high ohmage resistance 77 in the line 75 connecting the lead 70 to the ballast case S9 as a safety precaution, for example, in the event that the ungrounded lead 71 was inadvertently connected to the low potential lead 70 of primary winding 6l). It is to be understood that in normal operation the conducting fixture 6 is in circuit relation with the low potential side 72 of the alternating current source through grounds 73 and 74 and that the resistor 77, the line 75, and ground 76 serve no electrical function in a typically grounded system.

Having the structure and circuit of the lighting system in mind, the operation thereof will now be explained. When voltage is applied to the input leads 69, 70 of the primary 60, a voltage will be induced in the secondary winding 61 as determined by the respective turns ratio of the primary and secondary windings. The voltage induced in the secondary 61 is applied across the lamp through the cathodes thereof. Simultaneously therewith, the cathodes 15, 2.1 of the lamp are heated by cathode heating current from windings 63 and 62, respectively. Also, a series starting aid loop is formed including the primary 60, the secondary 61 connected in autotransformer relationship with the primary through low impedance line 64, and cathode 15 of the lamp, in capacitive relation with the conducting fixture 6. Starting with line 70, this loop passes through the primary 60, the line 64', the secondary 61, lines 67 and 68, the lamp holder 4, and the leads 13 and 14 to cathode 15. From the cathode 15 the starting aid loop continues through the capacitive coupling to the fixture 6 and thence is completed through ground 74 to ground 73 on the low potential side of primary 60. In this manner, the additive voltages of the primary and secondary are applied to cathode 15 of the lamp in autotransformer relation during starting. A small amount of current will flow from cathode 15 to the grounded fixture 6 thereby ionizing the gas in the area of the cathode. Due to the ionization of the gas, and in combination with the heating of the cathodes 15 and 21, the voltage induced in the secondary 61 and applied between the cathodes 15 and 21 of the lamp is sufficient to start the lamp. Once the lamp has started, only a minor circuit, from a current viewpoint, will be completed between cathode 15 and the fixture 6, and the ballast transformer apparatus will operate the lamp as a substantially isolated transformer.

The primary 60 and secondary 61 are wound on different parts of the magnetic core 58 and in my preferred ernbodiment are separated by a magnetic shunt 73 to provide a leakage path for magnetic fiux and thereby create leakage reactance. Such a ballasting transformer apparatus is a high reactance transformer and provides the additional function of limiting the current flow to the lamp L after the lamp has started. It will be understood that shunt 78 may be formed either through an air leakage path or through a leakage path of magnetic material, depending upon the design of the transformer.

A high impedance connecting the high potential side of the primary 60 and the low potential side of the secondary 61 becomes unnecessary as a safety precaution since the portions of the lamp holders 4, 5 and the lamp bases 2r, 3 which house the electrical contacts and inleads are so recessed that the fingers of a person mounting or dismounting a lamp while the lamp circuit may be unintentionally energized, are protected from accidentally touching electrically charged high voltage parts and thus receiving a lethal shock.

Referring now to the modfication of Fig. 3, there is illustrated a modification of the lighting system according to the instant invention wherein a single ballast transformer apparatus operates a pair of serially connected lamps. Each lamp, L1, L2, has a base 2 3 similar to the bases 2, 3` of lamp L described in connection with Fig, 1 above, and each lamp L1, L2 is held in a pair of lamp holders 4, 5 of the type 4, 5 described in connection with lamp L of Fig.` l above. Like numerals are used in Figs. 1 and 2 to identify similar parts.

The lighting system illustrated in Fig. 3 includes a ballast transformer apparatus, including a magnetic core 58 within a can or case 59 formed of conductive material. Primary Winding 60, secondary winding 6i, and cathode heating windings 62, 63 and 79 are positioned on the core. The secondary winding 61 may be spaced apart from the primary winding 6ft, and is separated therefrom by a magnetic shunt 78 thereby resulting in a high reactance transformer.

The ballast transformer apparatus is adapted to operate a pair of serially connected lamps L1 and L2. A first pair of output leads 80, S1 extend from the first cathode heating winding 62 for connection across one cathode 82 of lamp L1 through lamp holder 5 and a base 3. A second pair of output leads 83, 84 extend from the second cathodev heating winding 63 for connection across one cathode of the other discharge lamp L1 through lamp holder 4 and a lamp base 2. A third pair of output leads 86, 87 extend from the third cathode heating w-inding 79 for connection to the second cathode of each of the lamps; cathode 8S of lamp L2 and cathode S9 of lamp L1. The connection to lamp L2 is as shown through lamp holder 5 and base 3, and the connection to lamp L1 is through lamp holder 4 and base 2. The primary 60 has a pair of leads 69, 70 for connection to a source of alternating current voltage 71, 72. The low potential side 72 of the alternating current voltage would, as described above, normally be grounded as indicated by ground 73. The lamps L1 and L2 are in capacitive relation to a conducting part or fixture 6 which, in normal installation, would be grounded as indicated by ground 74 thereby completing a circuit between the low potential side of primary winding 60 and the conducting fixture 6. Connected between output leads 83 and 86 is a starting capacitor 90, so that the starting capacitor 90 is in parallel with the second discharge lamp L2. The low potential side of the secondary winding 61 is connected to the high potential side of the primary winding 60 by means of a line 64 having no significant impedance.

The operation of the circuit is similar to that of Fig. l. The additive voltages of the primary 60 and the secondary 61 are applied to the cathode 89 of lamp L1 in a starting aid circuit including the primary 60, the secondary 61, the starting capacitor 90, the cathode 89 in capaci-tive relation with the conducting fixture 6, the conducting fixture 6, and grounds '74 and 73. The starting capacitor 90 is of relatively low capacitance so that it does not draw appreciable current after lamp L2 has started, but its impedance is small compared to that of the capacitive coupling between the lamp L1 and fixture 6. Thus, it does not produce the major impedance in the starting aid circuit, and a very small current liows therein, determined principally by the impedance of the capacitive coupling with the fixture, to ionize the gas around cathode 89. A similar starting aid loop is formed for the lamp L2 with the additive voltages of the primary 60 and the secondary 61 being applied directly to the cathode 85, and the loop being completed through the capacitive coupling of the cathode 85 to the fixture.

Simultaneously, as voltage is applied in the starting aid circuit, the voltage of the secondary 61 is applied across the electrodes 82 and 89 of lamp L1 through a circuit comprising the lead 83, the starting capacitor 90, the lamp L1 itself and the leads 80 and 81 back to the low potential end of the secondary 61. In other words, the full voltage developed in the secondary 61 is placed across the cathodes 82 and 89 of lamp L1 and this, together with the ionized condition around the electrode causes lamp L1 to start.

After the lamp L1 has started, the second lamp L2 is then started by the loop comprising the secondary 61, lamp L1, and larnp L2 in a series starting circuit. Prior to the starting of lamp L2, the current fiow through lamp L1 yis minor, and the voltage drop thereacross is likewise minor as compared to the voltage drop across the capactor 90, so that substantially the full secondary voltage :is applied across the cathodes 85 and 88 of lamp L2. As described above, a minor current flow from cathode 85 to the conducting fixture is simultaneously ionizing the gas in the area of cathode 85 and this, in combination with the voltage across the lamp L2, is now sufficient to .start the lamp.

Once lamps L1 and L2 have started, the secondary 61 'operates them in a substantially isolated relation from the primary, the lamps being energized in an operating series circuit including only secondary 61, larnp L1, and lamp L2. The current flow through the starting capacitor f90 will be minor with reference to the current flow in the .operating circuit. Likewise, the current flow in the auxiliary starting aid circuit from the cathodes of lamps L1 and L2 to the conducting fixture 6 will be minor with reference to the current fiow through the operating circuit.

It will be readily appreciated that by the use of lamp holders and lamp bases having recessed contacts and inleads, the fingers of a person mounting or dismounting a lamp while the lamp circuit may be unintentionially energized, are protected from accidentally touching electrically charged parts.

It will also understood that while .both circuits shown utilize a ballast transformer having a high reactance, the invention may be advantageously used where a low reactance transformer is used and other ballasting means are provided. Also, while a rapid start circuit has been shown, that is, the electrodes are heated both before and after starting, the invention may be advantageously applied to other types of circuits, for example, to an instant start circuit. Further, while the illustrated modifications show all of the primary winding connected to all of the secondary so that their total voltages are combined in the starting aid circuit, if the total combined voltages of the primary and secondary are not needed, it would be sucient to add at least a portion of the primary winding to at least a portion of the secondary winding in the starting aid circuit.

Therefore, while this invention has been explained by describing particular embodiments thereof, it will be apparent that improvements and modifications may be made without departing from the scope of the invention as defined in the appending claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A lighting system for starting and operating at least one gaseous discharge lamp comprising at least one elongated gaseous discharge lamp having a sealed envelope with a base at each end, a cathode sealed in each end of said envelope, at least one inlead extending through each end of said envelope and having its inner end electrically connected to said cathode and having its outer end recessed in said base for protection from accidental con# tacts, a pair of lamp holders each having an opening therein and supporting said lamp in proximity to a conductive part, electrical contacts in said lamp holders engaging the respective inleads, said electrical contacts being recessed in said openings whereby said contacts are protected from accidental Contact therewith during mounting or disniounting of the lamp in the holders, a ballast transformer apparatus having a magnetic core, atleast a primary and a secondary winding on said core, means including said lamp holders and said inleads connecting said lamp across said secondary winding, a low impedance circuit connecting at least a portion of said secondary winding to at least a portion of said primary Winding in autotransformer relations with their respective voltages additive, input leads connected to said primary for connection to a source of alternating current voltage, and circuit means connecting the low potential side of the primary winding to the conductive part.

2. A lighting system for starting and operating a heated cathode discharge lamp comprising an elongated gaseous heated cathode discharge lamp having a sealed envelope with a base at each end, a cathode sealed within each end of said envelope, a pair of inleads extending through each end of said envelope and having their inner ends electrically connected to said cathodes and having their outer ends recessed in said base for protection from accidental contact, a pair of lamp holders each having 'an opening therein and supporting said lamp in a conductive fixture, a pair of electrical contacts in each of said lamp holders engaging the respective inleads, said electrical contacts being recessed in said openings for protection from accidental contact therewith during mounting or dismounting of the lamp in the holders, a ballast -transformer apparatus having a magnetic core, a primary Winding, a secondary winding, a first cathode heating winding, and a second cathode heating winding on said core, a first pair of output leads connecting the first pair of electrical contacts with said first cathode heating winding whereby said first cathode heating winding is connected to supply cathode heating current to one of the cathodes of said lamp, a second pair of outputleads for connecting the second pair of electrical contacts with the second cathode heating winding whereby said cathode heating Winding is connected to supply cathode heating current tin the second cathode of said lamp, said secondary winding being connected in circuit across said lamp, an electrical connection having no significant impedance betwee the -iow potential side of said secondary Winding and the high potential side of said primary winding whereby said windings are connected in -autotransformer relation with the voltages additive, a pair of input leads connected to said primary for connection to a source of alternating current voltage, and circuit means connecting the low potential side of said primary with said conductive fixture.

3. A lighting system for starting and operating a pair of gaseous discharge lamps comprising a pair of gaseous discharge lamps each having a sealed envelope with a base at each end, a cathode sealed within each end off each of said envelopes, at least one inlead extending through each end off each of said envelopes and having its inner end electrically connected to said cathode and having its outer end recessed in said base for protection from accidental contacts, a pair of lamp holders for supporting each lamp, each lamp holder having an opening therein and supporting its respective lamp in a conductive fixture, electrical contacts in each of said lamp holders engaging the respective inleads, said electrical contacts being recessed in said openings for protection from accidental contact therewith during mounting or dismounting if the lamp in the holders, a ballast transformer apparatus having a magnetic core, a primary winding and a secondary winding on said core, circuit means including said lamp holders and bases connecting said pair of serially connected lamps across said secondary winding, means for effecting sequential starting of said lamps, circuit means having no sign-iiioant impedance connecting the low potential end of said secondary winding and the high potential end of said primary winding in autotransformer relationship with their voltages ladditive, a pair of input leads on said primary Winding for connection to a source of alternating current voltage, and circuit means connecting the low potential side of said primary winding with the conductive fixture.

4. A lighting system for starting and operating a pair of gaseous discharge lamps comprising a pair of elongated gaseous heated cathode discharge lamps each having a sealed envelope with a base at each end, -a cathode sealed Within each end of each of said envelopes, a pair of inleads extending through each end if each of said envelopes and each having its inner end electrically connected to said cathode and having its outer end recessed in said cavity for protection from accidental contact, a pair of lamp holders for each lamp supporting said lamp in la conductive fixture, each of said lamp holders having an opening therein, electrical contacts in said lamp holders engaging the respective inleads, s-aid electrical contacts being recessed in said openings for protection from accidental contact therewith during mounting or dismounting of the lamp in the holders, -a ballast transformer apparatus having a magnetic core, a primary winding, a secondary winding, -a iirst cathode heating winding, Ia second cathode heating winding, and a third cathode heating Winding on said core, a iirst pair of output leads connecting the iirst cathode heating winding to one pair of electrical contacts for supplying cathode heating current to one cathode of one of said lamps, a second pair of output lines for connecting the second cathode heating Winding to a second pair of electrical contacts for supplying cath-ode heating Winding to one cathode of the other lamp, a third pair of output leads from said third cathode heating winding connected to the pair of electrical contacts in the second lamp holder in each of said lamps for supplying cathode heating current to the second cathode of each of said lamps, said secondary winding being connected across said serially connected lamps, a starting capacitor connected in parallel with one of said lamps, low impedance circuit means connecting the low potenti-al side of said secondary winding with the high potential side of said prim-ary winding in autotransformer relationship with the voltages additive, a pair of input leads on said primary winding for connection to a source of alternating current voltage, and circuit means connecting said conductive xture in electrical circuit relation with the low potential side of said primary Winding.

5. A lighting system for starting and operating at least one heated cathode gaseous `discharge lamp of the type having an elongated envelope with a base at each end and a cathode sealed in each end of the envelope and having a pair of inleads electrically connected to each cathode and extending through the envelope and having their outer ends recessed in the base for protection from accidental contacts, wherein the lamp is supported by a pair of lamp holders in close proximity to a conductive part and each having an opening therein containing a pair of electrical contacts recessed in the openings for p-rotection from accidental contact therewith during mounting or dismounting of the lamp in the holder, and wherein said pairs of contacts electrically engage the respective pairs of inleads; comprising, a magnetic core having at least a primary winding, a secondary winding, and cathode heating windings thereon, output leads on said cathode heating windings for connection to said contacts for supplying cathode heating current to said cathodes, means for connecting said lamp across said secondary winding Vthrough said lamp holders and said inleads, a low impedance circuit connecting the low potential side of said secondary winding to the high potential side of said primary winding in autotransformer relation with their respective voltages additive, input leads connected to said primary for connection to a source of alternating current voltage, and circuit means connecting the low potential side of said primary Winding to said conductive part.

References Cited in the file of this patent UNITED STATES PATENTS 2,455,791 Masciarelli Dec. 7, 1948 2,824,263 Strecker et al. Feb. 18, `1958 

